Patients with a definite diagnosis of this disease, as well as those patients who need confirmation of the disease, are candidates for this study. Patients will be admitted annually to the Clinical Center for a maximum of five days. A history will be taken and a physical exam done. Blood and urine tests will be done along with brain wave recording, complete eye examination, psychological tests, and speech and language and rehabilitation evaluations. A maximum of 3 mL/kg of blood will be drawn from children and a total of 60 mL from adults. Various eye tests will also be done, some under sedation. DNA will be extracted for possible use in other studies. A skin biopsy will be taken on the first visit.